TITLE: GCN CIRCULAR NUMBER: 18936 SUBJECT: GRB 160123A: GROND Upper limits DATE: 16/01/26 12:50:15 GMT FROM: John Graham at MPE/Garching J. F. Graham, T. Schweyer, and J. Greiner (all MPE Garching) report on behalf of the GROND team: We observed the field of GRB 160123A (Swift trigger 671447; Malesani, et al., GCN # 18926) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile). Observations started at 04:02 UT on 25 Jan 2016, approximately 43 hours after the GRB trigger, and lasted for 2 hours. They were performed at an average seeing of 1.64" and at an average airmass of 1.06. We do not detect a source within the Swift-XRT error circle reported by Beardmore et al. (GCN # 18927) down to (AB magnitudes) g' > 24.1 mag, r' > 24.4 mag, i' > 24.0 mag, z' > 23.9 mag, J > 21.3 mag, H > 20.9 mag, and K > 20.1 mag. The given limits are derived based on calibrating the images against GROND zeropoints and 2MASS field stars and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.10 in the direction of the burst (Schlegel et al. 1998).